A perfluoroalkanesulfonyl group (—SO2Rf) is known to be one of the most strongly electron-withdrawing groups. A bis(perfluoroalkanesulfonyl)methyl group (—CH(SO2Rf)2) containing two perfluoroalkanesulfonyl groups, in which perfluoroalkanesulfonyl moieties have a strong electron-withdrawing property, tends to release H and therefore exhibits high acidity.
For example, bis(trifluoromethanesulfonyl)methane (CH2(SO2CF3)2) and phenylbis(trifluoromethanesulfonyl)methane (PhCH(SO2CF3)2), either of which contains bis(trifluoromethanesulfonyl) group (—CH(SO2CF3)2), are known as strong acids.
In Patent Publications 1 and 2, there is disclosed the introduction of a bis(perfluoroalkanesulfonyl)methyl group to an aromatic compound for the purpose of acquiring an acid catalyst.
In Patent Publication 1, a phenol-based compound containing bis(trifluoromethanesulfonyl)ethyl group is disclosed as a nontoxic acid catalyst that can reduce wastes in the synthesis without subjecting a reactor to corrosion. In order to obtain an aromatic compound containing bis(trifluoromethanesulfonyl)ethyl group, 1,1,3,3-tetrakis(trifluoromethanesulfonyl)propane ((CF3SO2)2CHCH2CH(SO2CF3)2) is used and bis(trifluoromethanesulfonyl)ethyl group is introduced into an aromatic phenol derivative or aromatic amine derivative. This reaction utilizes bis(trifluoromethanesulfonyl)ethylene ((CF3SO2)2CHCH2) which is generated from 1,1,3,3-tetrakis(trifluoromethanesulfonyl)propane in the reaction system and has high activity, thereby enabling a compound containing bis(trifluoromethanesulfonyl)methyl group to be produced under moderate conditions, from a wide variety of substrates, with high yield.
However, 1,1,3,3-tetrakis(trifluoromethanesulfonyl)propane requires two equivalents of bis(trifluoromethanesulfonyl)methane, and it is necessary to synthesize this compound separately. Moreover, there has been a problem in view of efficiency that, when bis(trifluoromethanesulfonyl)ethylene generates, an equal amount of bis(trifluoromethanesulfonyl)methane is formed as a by-product.
In Patent Publication 2, there is disclosed a polymer support type arylbis(perfluoroalkylsulfonyl)methane represented by the general formula (RCH(SO2Rf)(SO2Rf′)) (where R represents a substituted or unsubstituted aryl group and Rf and Rf′ mutually independently represent a perfluoroalkyl group). The polymer support type arylbis(perfluoroalkylsulfonyl)methane can improve the efficiency of a reaction proceeding in the presence of a Broensted acid or a Lewis acid catalyst, for example, facilitates the benzoylation of an alcohol, and can easily be recovered or recycled. Furthermore, Patent Publication 2 mentions that the polymer support type arylbis(perfluoroalkylsulfonyl)methane is usable as a solid catalyst excellent from the viewpoints of toxicity, environments and the like.
In order to obtain the polymer support type arylbis(perfluoroalkylsulfonyl)methane, however, the raw material is limited to a high active aryl halide and requires an excessively large amount of an activating reagent such as a trifluoromethane sulfinate and an easily hydrolizable trifluoromethanesulfonic anhydride and requires to go through a multistage synthetic route under a low temperature and strongly basic condition, which has brought about a problem of complicated synthesis operations.
The introduction of a bis(perfluoroalkanesulfonyl)methyl group into an aromatic compound has thus been reported, but the introduction of a bis(perfluoroalkanesulfonyl)methyl group into an aliphatic compound has been mentioned in a few reports, for example, in Non-Patent Publication 1 and Non-Patent Publication 2.
In Non-Patent Publication 1, there is described a method of producing 1,1-bis(trifluoromethanesulfonyl)octane where octanol (C8H17OH), trifluoromethanesulfinyl chloride (CF3SOCl) and trifluoromethanesulfonic anhydride ((CF3SO2)2O) are used as raw materials. However, this method causes a multistage reaction requiring much expense in time and effort to be controlled, which reaction is developed in use of an activating reagent not ordinary, and therefore confronts a problem that 1,1-bis(trifluoromethanesulfonyl)octane is not obtained with high yield.
Additionally, Non-Patent Publication 2 discusses a method of introducing a bis(trifluoromethanesulfonyl)methyl group into an aliphatic epoxide compound, in which a Grignard reagent prepared from bis(trifluoromethanesulfonyl)methane and methylmagnesium chloride is reacted with epoxide to prolong the alkyl side chain. However, epoxide is not ordinary and highly decomposable to be used as a raw material, and dehydration conditions adopted at the time of using the Grignard reagent are restricted, and therefore this method is difficult to say a practical one.
Thus, a compound having a bis(perfluoroalkanesulfonyl)methyl group exhibits a high acidity and a hydrophobicity and therefore usable as an acid catalyst and the like. However, a production of a compound having a bis(perfluoroalkanesulfonyl)methyl group bears some problems in that: the synthesis of a raw material is not easy; it requires a multistage stage; and a compound (a reagent) to be reacted with the raw material is unstable and therefore has to be used in an excessively large amount, for example.
Moreover, in U.S. Patent Publications 3 to 5, there is disclosed a method for producing a bis(trifluoromethanesulfonyl)ethylene derivative by a condensation reaction between bis(trifluoromethanesulfonyl)methane and an aldehyde derivative. The raw material is an aromatic aldehyde, a conjugated aldehyde, acetaldehyde or paraformaldehyde, from which the following bis(trifluoroalkanesulfonyl)ethylene compounds are synthesized.

A resin film containing a bis(perfluoroalkanesulfonyl)methyl group (—CH(SO2Rf)2) is known to be usable as a solid electrolyte membrane for a polymer electrolyte fuel cell (hereinafter, sometimes referred to as PEFC).
More specifically, a polymer electrolyte fuel cell uses an ion exchange resin membrane (a solid electrolyte membrane) as an electrolyte. Among polymer electrolyte fuel cells, a direct methanol fuel cell (hereinafter, sometimes referred to as DMFC) uses methanol as fuel instead of hydrogen, in which methanol is directly reacted at electrodes to generate electricity. On the contrary to other fuel cells where electrons are released from hydrogen by the action of catalyst on the side of anode (or the side of fuel electrode) thereby separating hydrogen into hydrogen ions (protons) and electrons, in a direct methanol fuel cell methanol is directly reacted with water by the action of catalyst on the anode side to be converted into protons, electrons and carbon dioxide.
As one of objects of the direct methanol fuel cell, it is possible to cite a crossover phenomenon in which a part of methanol permeates through a solid electrolyte from an anode side (a fuel electrode) toward a cathode side (an air electrode). With this phenomenon, fuel is lost and additionally oxygen is consumed by methanol on the air electrode side so as to cause power decline. Hence a development of a solid electrolyte membrane not causing such a methanol permeation is the most important object for sophisticating the performance of a direct methanol fuel cell. In usual cases a resin having a sulfonic acid group is used in a solid electrolyte membrane; however, this membrane holds water firmly by the sulfonic acid group having a strong hydrophilicity, so that the dispersion of methanol is accelerated to enhance methanol permeation.
Patent Publication 6, discloses a solid electrolyte membrane into which a bis(perfluoroalkanesulfonyl)methyl group is introduced, as a solid electrolyte membrane having both a high proton conductivity and a low methanol permeability for suppressing a crossover phenomenon of methanol. By introducing a polyether structure that can be coordinated with water by van der Waals force into a repeating unit containing a hydrophobic and strongly acidic bis(perfluoroalkanesulfonyl)methyl group as an acidic group, it becomes possible to exhibit a high proton conductivity and a low methanol permeation.